Traditionally, subsea wells located on the seabed comprised well casing extending into the earth, a wellhead coupled to the casing and located at the seabed, a valving system commonly known as a Christmas tree coupled to the wellhead, and a flowline extending from the Christmas tree to the surface. In more recent times, templates have been used which are located on the seabed and which can support a plurality of Christmas trees and wellheads communicating with a plurality of wells. Typically, these templates are pre-piped to provide flow line and hydraulic line interconnection between the Christmas trees supported on the template. Unfortunately, if these hydraulic and flow lines on the template are damaged and the template is below diver depth, the entire subsea production system has to be shut down permanently Such damage to these lines can occur due to earthquakes, equipment falling from surface vessels and the like.
Accordingly, it is highly advantageous to arrange such a subsea well system in which the hydraulic and flow lines used with the Christmas trees can be retrieved. While this is broadly known in the prior art, the prior art attempts have not met with considerable success since they are complicated and usually need diver intervention.
Examples of these prior art devices are disclosed in the following U.S. Pat. Nos.: 3,633,667 to Falkner, Jr.; 3,777,812 to Burkhardt et al.; 3,877,520 to Putnam; 3,881,549 to Thomas; 3,987,638 to Burkhardt et al.; 4,036,295 to Kirkland et al.; 4,120,362 to Chateau et al.; 4,192,383 to Kirkland et al.; and 4,194,857 to Chateau et al.
Accordingly, there is a continuing need for improvement in such well systems.